Principles of Synchronous Digital Hierarchy

11Introduction

individual channels in the transmission media. Thus, a at 4-kHz band-

width is used for each channel.

1.8 Multiplexing Structure of FDM Schemes

In the previous section, we have seen the conceptual design of a four-channel

multiplexer. In practice the minimum number of channels dened for a mul-

tiplexer is 12. This group of 12 channels is called a “basic group” and is of

12× 4 = 48-kHz bandwidth. The basic group’s frequency range is dened

as 60 to 108 kHz (and not 4 to 52 kHz), and the rst channel is on the top

frequency, as per the standards dening body in telecommunication, the

International Telecommunication ...